Certain fungal metabolites exhibit antitumor and antiviral activity. A number of the important agents of this type can be grouped together as a single class inasmuch as they all contain the epidithiodiketopiperazine moiety. Prominent members of this class include gliotoxin, aranotin, acetylaranotin, chaetocin, and sporidesmin. The structures of these substances have been established by x-ray crystallographic analyses and by chemical studies. It is proposed to undertake the total syntheses of these substances and certain derivatives to provide compounds for testing as potential new and useful antitumor and/or antiviral agents. The synthetic approach envisioned will entail the preparation of oxepine and dioxepine (arene mono- and diepoxide) derivatives thought to be intermediates in the biogenesis of gliotoxin and aranotin. A new reaction effecting indole dimerization will be explored as a possible route to the synthesis of chaetocin.